NEWS | Legislation
Fire Effects on Noxious Weeds
By Robin Innes, Ecologist Writer for the Fire Effects
Information System
The Fire Effects Information System (FEIS, www.fs.fed.
us/database/feis/) has been providing reviews of
scientific knowledge about fire effects since 1986. FEIS
is an online collection of literature reviews on more than
1,100 species and their relationships with fire. Reviews
cover plants and animals throughout the United States,
providing a wealth of information for landowners and
resource managers.
The Fire Effects Information System recently completed
a multi-year project to increase the information available
in FEIS on nonnative invasives in the United States.
There are more than 100 reviews available on
nonnative invasive plants in Montana, including 25
species on the Montana Noxious Weed List.
Literature reviews and syntheses are important sources of information for land managers who need detailed
information about invasive species and their relationships to fire. This is particularly relevant during a year, such as
this one, of extensive wildfires in Montana and throughout the West.
Reviews published in FEIS synthesize information on the biology and ecology of individual plant species, especially
regarding: •
How invasive plant species may respond to fire and thus influence native plant communities
•
How fire, fire suppression activities, and fire exclusion may influence plant invasions and site invasibility
•
How invasive plants may alter fuels and fire regime characteristics
•
Knowledge gaps and limitations of existing knowledge on these topics
Leafy spurge, common tansy, and yellow and Dalmatian toadflaxes are examples of Montana invasives reviewed in
FEIS. The following excerpts are from these FEIS reviews:
Leafy spurge: Leafy spurge has a large, deep, and highly regenerative root system, which makes sprouting of
established plants after fire nearly certain. Because very deep leafy spurge roots are capable of sprouting, even
severe fires are not likely to kill mature plants. Leafy spurge seeds can be killed by fire, but depending upon fire
timing, fire severity, and depth of seed burial, many may survive. The high oil content of leafy spurge foliage may allow
for good fire spread. Although prescribed fire alone is not used to control leafy spurge, fire in conjunction with
herbicides has provided some control, and fire may improve the effectiveness of flea beetle biocontrols.
Common tansy: Common tansy is likely only top-killed by fire. On sites with established common tansy plants,
postfire sprouting from rhizomes is likely the predominant regeneration method. Because common tansy seeds can be
dispersed long distances and seedlings establish best on sites with bare ground, little established vegetation, and high
light levels, burned areas could provide suitable establishment sites. Although no studies (as of 2009) directly reported
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8 |Fall
Weed Times
Fire and weeds....
NEWS | Legislation
on common tansy’s response to fire, some sources suggest that fire may result in increased abundance or facilitate
spread of common tansy. If common tansy plants are burned at the flowering stage, surviving seeds may produce
mutated seedlings. Dense patches of dried common tansy stems may burn intensely. Altered fire regimes in common
tansy habitats were not reported, but fuels in dense patches of the previous year’s stems may change fire behavior or
increase fire severity in areas with an abundance of common tansy. Prescribed fire in the spring may reduce future
fire potential in common tansy stands. Prescribed fire alone is not likely to control common tansy. However, fire may
be useful in removing dead stems and litter and increasing common tansy’s exposure to herbicide treatments or grazing. Fire may also be used to dispose of stems with flowers or seeds on mowed or cut sites, because on-site destruction of reproductive stems should decrease the potential for dispersal and spread.
Yellow and Dalmatian Toadflax: Yellow and Dalmatian toadflaxes are likely to be top killed by fire, however their deep,
extensive root systems are likely to survive even severe fire and allow reestablishment of populations from vegetative
buds on roots. Scorching of floral stalks by fire may prevent seed production during the first postfire year. Toadflaxes
are able to quickly recover after fire and may even be promoted by fire, especially if other species are reduced. The
postfire environment is well suited to toadflax establishment by seed. Most literature suggest that toadflaxes are likely
to increase or to be unaffected by fire. Burning is not usually a recommended or effective control method for toadflaxes because root buds and buried seeds are unaffected by fire and burning may increase competitiveness of toadflax
by removing desirable plants. Removal of toadflax top-growth may even stimulate production of vegetative shoots.
Because of their propensity to establish in dry, open areas with little plant competition, toadflaxes have high potential
for establishing after fire (when competition from other vegetation is removed or reduced) either by seed imported to
the site or by soil-stored seed.
A snake dance?
DEQ Employee Pat Plantenberg observed a “snake dance” while
spraying for noxious weeds. Plantenberg was at the reclaimed
Spokane Minerals limestone quarry on McMasters’ Ranch
when he came upon the two male rattlers engaged in the dance.
No, not the tango or the waltz, this dance is to determine which
rattler is dominant! When two males encounter one another
during mating season they raise up their bodies and “dance” until
one is able to force the other to the ground. The winner of this
combat gets breeding rights. Plantenberg was able to observe and
take pictures of the snakes for over 10 minutes from 10 to 15 feet
away. They weren’t paying him any attention and were still in
combat when he left to continue his weed spraying!
Fall Weed Times | 9